Evidence for chemical changes on the root surface of tall fescue in response to infection with the fungal endophyte Neotyphodium coenophialum

摘要

In a growth chamber experiment, tall fescue (Festuca arundinacea) genotypes DN2, DN4, DN7 and DN11, infected with their naturally occurring strains of N. coenophialum (E+), and their non-infected isolines (E-), were cultivated in nutrient solution at 2 P levels: 31 ppm (P+) or 0 ppm (P-) for 4 weeks. Endophyte infection significantly increased the Fe3+ reducing activity rate of extracellular reductants (9.6 X 10-3μmol Fe3+ h-1 g-1 root fresh weight (FW)) compared with E- plants (3.9 X 10-3) and Fe3+ reduction rate of intact root tissues (6.16 and 4.48μmol Fe3+ h-1 g-1 root FW for E+ and E- plants, respectively). In response to P deficiency, Fe3+ reduction rate of intact root tissues increased in E+ plants by 375% compared with E- plants, whereasno significant differences were observed when P was provided. Total phenolic concentration was 20% greater in shoots of E+ plants than in E- plants. In response to P deficiency, total phenolic concentration increased in roots of E+ plants by 7%, and decreased in roots of E- plants by 10%. The most active Fe3+ reducing zones were located along branches of secondary and tertiary roots.